Nanostellar have announced the launch of their NS Gold catalyst which is reported to improve hydrocarbon oxidation activity over traditional platinum group metal products.

Air pollution from vehicles is the most important field of application for precious metal catalysts. The three main pollutants emitted from internal combustion engines are carbon monoxide, hydrocarbons and nitrogen oxides. Catalysts capable of removing these three pollutants are termed three way catalysts (TWCs). Commercial TWC's are based on platinum-group metals (PGM’s); platinum, palladium and rhodium and over 200 tonnes per year of these metals are used in automotive catalysts. Catalyst systems based on the PGMs perform the task of emission control very well and are able to meet current legislative emission targets. Many aspects of this technology are very well established, with cost reduction rather than performance improvement perhaps the most important issue for future development.

The comparatively low melting point of gold (1064 °C, compared with 1769 °C for platinum) means that the material is not suitable for use in TWCs that operate at high temperatures (>600 °C). However, if there is found to be scope to improve the thermal durability of gold-based catalysts gold catalysts could potentially be stabilised for at least application in lower temperature applications eg diesel exhaust systems. For example, Nanostellar, Inc., have recently announced a first in diesel emissions technology: the introduction of gold as an oxidation catalyst. Independent testing of Nanostellar’s NS Gold™, in comparison with today’s pure-platinum catalysts, has shown that NS Gold™ increases hydrocarbon oxidation activity by as much as 40 percent at equal precious-metal cost. When compared to emerging platinum-palladium catalysts, NS Gold™ promises to increase hydrocarbon oxidation activity by 15-20 percent at equal precious-metal cost. A tri-metalllic formulation of gold, platinum, and palladium, NS Gold™ allows the proportions of each metal to be adjusted to help catalyst systems engineers meet engine-specific performance targets and stabilize the overall cost of diesel catalysts, despite fluctuations in the price of precious metals.

According to Nanostellar NS Gold™ is potentially suitable for treating all lean-stream exhaust, where air is in excess of fuel-borne hydrocarbon gases. Applications include, but are not limited to, treating particulates and hydrocarbons in soot filters, stationary-source volatile organic compound (VOC) emissions, and ammonia slip in selective catalytic reduction (SCR) systems. NS Gold™ is immediately available for targeted application-specific testing. See www.nanostellar.com for more details.

At the end of 2007, World Gold Council and Nanostellar announced a strategic partnership to promote the NS Gold™ technology.